This invention relates to semiconductor materials. More particularly, it is concerned with heteroepitaxial semiconductor structures and methods of manufacturing.
Recently there has been increased interest in various electronic and opto-electronic devices fabricated in heteroepitaxial semiconductor structures; that is, semiconductor structures employing a substrate of one semiconducting or insulating material with an epitaxially grown layer of a different semiconductor material on the substrate. One significant problem in structures of this type is the presence of stress in the plane of the epitaxially grown layer. The epitaxially grown layer is unstressed at the growth temperature which typically is about 600.degree. C. Upon cooling, however, stress is produced in the epitaxial layer because of the difference in the coefficients of thermal expansion of the substrate material and the epitaxially grown layer. The presence of such stress has a significant effect on devices fabricated in the heteroepitaxial structure. The stress causes modification of the band structure of the epitaxially grown material and thus affects both the optical and electrical properties of the semiconductor material of the layer. In addition, there may be stress-induced migration of dislocations in the crystal structure of the epitaxial layer causing degradation of opto-electronic devices fabricated in the heteroepitaxial structure.